Qu'vat virus
- Genetically-modified virus originally intended to introduce Human Augment sequences to the Klingon genome (ENT: "Affliction")
- Created June 2154 as covert military project with a limited pool of test subjects using embryos recovered from the wreckage of a destroyed Augment-commandeered bird-of-prey at Qu'Vat Colony (ENT: "Affliction")
- Tests proved unreliable
- While strength and intelligence were increased, virus also introduced physical changes, resulting in Klingons who largely resembled Humans (ENT: "Affliction")
- Viral strain was ultimately fatal due to in breakdown of neural connections as a side effect of introduced neurological changes (ENT: "Affliction")
- Further, virus became exposed to Levodian flu virus upon introduction to a test subject unknowingly infected (ENT: "Affliction")
- Horizontal gene transfer resulted in genetic modifications becoming embedded in flu virus (ENT: "Affliction")
- New virus maintained genetic and structural modifications, but entered a contagious phase shortly before widespread neurological re-ordering (ENT: "Affliction")
- Epidemic resulted, leading to millions dead (ENT: "Affliction")
- Early attempts at containing the epidemic were largely military (ENT: "Affliction")
- Direct strikes at infected colonies to wipe out infected populations (ENT: "Affliction")
- N'Vak Colony destroyed in the process (ENT: "Affliction")
- Direct strikes at infected colonies to wipe out infected populations (ENT: "Affliction")
- Overall progression:
- Stage 1: Initial physical and neurological changes, including dissolution of cranial ridges and minor personality modifications
- Stage 2: Becomes contagious, able to spread via air or physical contact
- Stage 3: Widespread modifications to physical and neurological structure
- Stage 4: Uncontrolled neurological changes progress into neuron breakdown, leading to death
- Cure developed November 2154 by combined efforts of Phlox and Antaak (ENT: "Divergence")
- Specific method of action stabilized Augment/Levodian flu virus at stage 1, preventing contagion and death (ENT: "Divergence")
- While fatal epidemic was averted, stage 1 infection introduced heritable physical changes resulting in formation of a minority caste - known as QuchHa' - in Klingon society (TOS)
- Minority caste continued to exist until early 2290s upon discovery of a full cure for the virus
- Existence of QuchHa' seen as an embarrassment to Klingon society, largely forgotten to the point that by 24th century, even Federation medical experts unaware of this phase of Klingon history (DS9: "Trials and Tribble-ations")